To enhance internal-signal transmission efficiency for a control device used to drive a load, a system is proposed that uses serial communication to transmit control signals from a processor to a driving circuit including a switching element. During the serial communication, the superimposition of minuscule noise, which may not be taken into consideration in a transmission system based on a parallel communication, is problematic because a large number of control signals are transmitted through one serial communication line. As described in JP-1994-204989-A (Patent Document 1), accordingly, a technique for transmitting or receiving the same data twice in succession is proposed for improvement in the reliability of communication.